Control and modulation of intracellular reduction and oxidation (redox) environment is of fundamental relevance for cellular processes. For example, loss in the redox control of the cell cycle can lead to a more oxidant environment, promoting the progression from G1 to S phase and therefore leading to aberrant proliferation, a hallmark of various neoplasies. Also, most chronic inflammatory diseases are accompanied by a loss of redox control. Dysregulation towards a more oxidized intracellular environment is thus associated with aberrant proliferation and inflammation and is therefore ultimately related to diseases such as, but not limited to, cancer, neurodegenerative disease, diabetes, aberrant wound healing, and fibrosis. In addition, in oxidative environments, proteins can be oxidative modified, a process often followed by the formation of aggregates, also in the form of amyloids.
The functional status of cells is under the control of external stimuli, affecting the function of critical proteins and gene expression. Signal sensing and transduction by messengers to specific effectors operate by post-translational modification of proteins, among which thiol (—SH) reduction/oxidation (redox) switches play a fundamental role. Sensitive cysteine residues in proteins constitute the mentioned redox switches, where “sensitive” indicates a lower electrochemical potential of the cysteine/cystine redox couple (SH/S—S) resulting from a specific protein conformation. Thiol redox switches in for example enzymes, receptors, transporters, transcription factors, structural elements, regulators of protein trafficking synthesis and degradation, and the cytoskeletal structure all deeply affect the overall cellular homeostasis.
The production of oxidants in mammalian cells derives from fundamental processes such as glycolysis and mitochondrial respiratory chain, ending up with the production of reactive oxygen species, among them the most stable is represented by hydrogen peroxide (H2O2). The produced oxidants must be under a strict control and a reversal of the oxidative pathway is necessary. The redox control is affected by several low molecular weight substances and a complex network of enzymes, including among others, glutathione reductase (GR) and the family of selenium-dependent glutathione peroxidases (GPx). Reduced glutathione (GSH) is a dominant low molecular weight thiol species in most organisms, whose redox potential is used by the many enzymes in charge of the redox control in cells, including GR and GPx, to recycle their own redox status.
Reduced glutathione (GSH) is a tripeptide present in all human tissues at relatively high concentrations, even above 10 mM. It has many important functions in the body. As described above, it can be regarded as the major endogenous antioxidant, participating: 1) in the control of the cell redox status; and 2) in the control of the oxidation status of proteins relevant in signaling, including the receptors of external stimuli (e.g. hormone receptors). It plays a fundamental role in numerous metabolic and biochemical reactions such as DNA synthesis and repair, protein synthesis, prostaglandin synthesis, amino acid transport, and enzyme activation. It also participates in the regulation of the nitric oxide cycle, detoxifies many carcinogens and other xenobiotics and has an essential role for optimal response in many parts of the immune system. Thus, most systems in the body can be affected by the state of the glutathione system. For instance, states of glutathione deficiency include HIV/AIDS, chemical and infectious hepatitis, prostate and other cancers, cataracts, Alzheimer's disease, Parkinson's disease, chronic obstructive pulmonary disease, asthma, radiation poisoning, malnutritive states, arduous physical stress and aging, and has been associated with suboptimal immune response. Low glutathione is also strongly implicated in wasting and negative nitrogen balance, as seen in cancer, AIDS, sepsis, trauma, burns and even athletic overtraining, as well as in bipolar disorder, major depressive disorder, and schizophrenia.
Glutathione is synthesized from the amino acids L-cysteine, L-glutamic acid and glycine. The sulfhydryl (thiol) group (SH) of the cysteine serves as a proton donor and is responsible for the biological activity of glutathione. The supply of cysteine is the rate-limiting factor in glutathione synthesis by the cells, since cysteine is a relatively rare nutrient. Glutathione supplementation has thus been suggested for various diseases and symptoms.
However, glutathione taken orally can be degraded already in the stomach and is not well absorbed across the gastrointestinal tract. Thus raising glutathione levels through direct supplementation of glutathione is difficult. Instead supplements of agents that serve as glutathione precursors are used to increase the plasma concentration of glutathione. N-acetyl-L-cysteine (NAC in the following) is a simpler molecule than glutathione, diffuses freely in almost all tissues and cells and is the most bioavailable precursor of glutathione. Among the several thiol agents tested for their efficacy in modulating cellular redox status, NAC holds most promise for human use. A relevant advantage in the clinical use of NAC is the virtual absence of side effects. This compound has been long available for the clinic as a mucolytic agent and as an antidote after paracetamol poisoning.
In recent years NAC has also been acknowledged as having other beneficial properties. For example, NAC has been reported to have an anti-inflammatory effect and has been added to the family of non-steroidal anti-inflammatory drugs (NSAIDs). The inventors of the present disclosure have previously shown that in mammalian cells, in vitro, NAC inhibits proliferation and promotes quiescence, further evolving in terminal differentiation (WO 02/051405 A1, T. Parasassi, et. al. (Cell Death and Differentiation (2005), Vol. 12, No. 10, pages 1285-1296); E. K. Krasnowska et. al. (Free Radicals Biology and Medicine 2008, 45(11):1566-72) and A. C. Gustafsson et. al. (BMC Cancer (2005), 5:75). NAC has in this context been found to possess a marked antiproliferative effect on cancer cells and has also been found to be effective in the treatment of endometriosis. Additionally it has been used in the treatment of polycystic ovary syndrome (PCOS) as well as for treatment of various other diseases and conditions, e.g. as a nephroprotective agent, interstitial lung disease, schizophrenia, bipolar disorder and depression, and has been suggested for various other uses.
Thus, NAC is effective for many uses. Nevertheless, prolonged NAC treatments result in a decreased plasma level of NAC, so that its effective concentration must be increased and the risk of undesired side effects accordingly increases (L Pendyala and P J Creaven, Cancer Epidemiol Biomarkers Prev 1995; 4:245-251). In order to counteract the declining effect of NAC, pulsed treatments were proposed, to allow for a washout period. Another possible solution would be of reducing the concentration at which NAC is effective, which would be advantageous also for short term treatments.
There has been a wide recent interest in the protecting and/or therapeutic role of both selenium (Se in the following) and melatonin (Mel in the following). Se supplementation has for example been suggested for prevention of cancer, as an antioxidant or immune enhancer. Likewise, melatonin has been studied for the treatment of cancer, immune diseases and various other disorders. Despite this, controversial effects of these two substances were also reported. For instance, Mel has been acknowledged for its antioxidant action, but was sometimes also reported to act as a pro-oxidant (Cemeli E, Baumgartner A, Anderson D. Mutat Res. 2009; 681:51-67; Wölfler A, Caluba H C, Abuja P M et al. FEBS Lett. 2001; 502(3):127-31; Radogna F et al. Toxicology and Applied Pharmacology 2009; 239:37-45).
Regarding Se, a large trial showed that the expected prevention of prostate cancer or of other cancers was not achieved (Lippman S M et al., Journal of American Medical Association. 2009; 301(1):39-51). EAKlein (J Natl Cancer Inst. 2009; 101: 283-285) concluded with the cautionary lesson that “well-performed large-scale controlled trials do not always validate what we believe biology indicates and that our model systems are imperfect measures of clinical outcomes in the real world.” Also, although a preventive role of Se on the risk of diabetes was reported and ascribed to its “insulin-like” activity and to the antioxidant properties of the selenoenzymes, a prospective study did not report any significant relationship between selenium and the risk of diabetes (Akbaraly T N et al., Nutr Metab (Lond). 2010; 7:21).
Balansky et al., “Interactions between N-acetylcysteine and sodium selenite in modulating the clastogenicity of urethane and 2-acetylaminofluorene in mice”, Int. J. Cancer, Vol. 108, 2004, pp. 158-161, discloses the use of a combination of NAC and Se for attenuating the adverse effects of cytotoxic drugs and chemopreventive agents in the treatment of cancer.
Safarinejad et al., “Efficacy of selenium and/or N-acetyl-cysteine for improving semen parameters in infertile men: a double-blind, placebo controlled, randomized study”, J. Urol., Vol. 181, No. 1, 2009, pp. 741-751, Epub December 2008, discloses the use of NAC and Se in combination or separately for improving semen quality in infertile men. Administering NAC and Se in combination resulted in additive beneficial effects.
Yalçin et al., “Synergistic action of sodium selenite and N-acetylcysteine in acetaminophen-induced liver damage”, Hum. Exp. Toxicol., Vol. 27, No. 5, 2008, pp. 425-429, discloses the use of NAC and Se in combination or separately for treatment of acetaminophen overdosing. NAC and Se in combination were found to give better protection against hepatotoxicity compared to either agent alone.
Emonet et al., “Thiols and selenium: protective effect on human skin fibroblasts exposed to UVA radiation”, J. Photochem. Photobiol., Vol. 40, No. 1, 1997, pp. 84-90, discloses the use of NAC and Se in combination to protect cells against UVA damage.
Look et al., “Sodium selenite and N-acetylcysteine in antiretroviral-naive HIV-1-infected patients: a randomized, controlled pilot study”, J. Clin. Invest., Vol. 28, No. 5, 1998, pp. 389-397, discloses a combined oral administration of NAC and Se with the objective to improve blood count and reduce viral load in patients with HIV.
Sener et al., “Melatonin and N-acetylcysteine have beneficial effects during hepatic ischemia and reperfusion”, Life Sciences, Vol. 72, 2003, pp. 2707-2718, discloses the use of NAC and Mel alone or in combination to treat hepatic ischemia. Mel was found more potent than NAC, and the combination of the two was found to be more effective than either alone.
WO 03/077900 A1 and US 2005/0164911 A1 disclose a method for preventing the development of cancer or neurodegenerative diseases by administering NAC, melatonin, or a combination thereof, as well as a medicament comprising NAC and Mel.
WO 00/531376 describes a composition containing cysteine, selenium and melatonin together with a number of other components. US 2007/0231312, US 2011/027771, WO 98/33494 and U.S. Pat. No. 6,207,190 all describe different formulations containing among other things, NAC, Se and Mel. Further, US 2004/045566 describes a composition containing glutathione, selenium and melatonin for absorbing dangerous component from tobacco smoke. None of the said documents describes the use of selenomethionine.
In all documents referred to in the prior art selenium is used as such.